Recently, various types of electronic devices for office automation and the like have been installed, especially in offices and so forth. The installation of the wiring for these electronic devices is generally carried out separately from the interior construction, so that the simplest installation method involves the use of cables lying on the surface of the floor. However, &he laying of a number of cables on the surface of the floor leads to an unsightly appearance and decreases safety, so that such installation is inconsistent with the attainment of an ideal office or living space, which has been recently increasingly in demand.
This installation can also be carried out by using two layers in the construction of the floor and installing theses cables beneath the upper floor surface. Conventionally, the construction of such double floors is such that alterations to the walls or floor foundation are not necessary; in other words, a number of legs are formed on the rear surface with a fixed spacing, and above this panels are laid closely together to form the floor.
However, since the legs of the panels used conventionally for the construction of such double floors are formed integrally with the panel bodies, the length of the legs cannot be changed without changing the whole of the panel, so that the changing of the floor height, for example when the number of cables increases, involves a great deal of labor. Furthermore, if unevennesses exist in the surface below the floor, corresponding unevennesses may be formed in the floor surface constructed above this, so that the underlying surface must be leveled and unevennesses removed.
It might be thought that simply by making the legs freely detachable from the panels, thus allowing their length to be altered, this type of problem could be solved. However, in this case, the problem of "instability" or "creaking" occurs as a result of play in the attaching elements, and the altering of the length of the legs cannot be easily accomplished.
Furthermore, in this type of double floor, and especially in the case in which the width (space from wall to wall) or shape of the floor surface is peculiar, it is difficult to lay panels of standardized dimensions over the whole floor surface without leaving gaps. Conventionally, other materials having the same height as the panels have been used to fill in at the floor edges.
These materials used to fill in at the edges of the floor surface must be fitted to the existing gaps at the site in the proper dimensions and form; there is a particular problem in that the creation and installation of these materials in cases in which their shape is complex, as when there is a pillar protruding from a wall surface or the like, takes a great deal of work.
In addition, the method of determining the strength of such panels for double floors is conventionally such that the strength is set in correspondence with an area load calculated on the basis of the largest weight by area among the machines to be placed on the floor; panels possessing this degree of strength are used over the entire surface of the floor.
As a result of this, especially when heavy items are to be placed on the floor, since high-strength panels are used over the entire floor surface, the cost of constructing the double floor is very high.